The present invention relates to a surface processing method for etching the surface of a work, such as a glass substrate or a semiconductor substrate, or for depositing a film of a material over the surface of a work and, more specifically, to a novel surface processing method employing submicron particles.
The fabrication of a functional element, such as a semiconductor integrated circuit chip, a printed circuit board or a magnetic head, requires various minute processing techniques such as advanced etching techniques or thin film forming techniques.
Under such circumstances, researches have been conducted in various fields and there have been developed advanced processing techniques employing a resist mask for etching the surface of a semiconductor wafer, such as an ion beam etching method (IBE) using electrically accelerated argon ions for physically etching the surface of a work and a reactive ion etching method (RIE) using activated fluorine or chlorine gas for physically and chemically etching the surface of a work.
The processing rates of those etching methods are relatively low, need an expensive apparatus and requires troublesome work for the maintenance of the apparatus.
A noteworthy sandblasting method in which grit is blown together with compressed air is proposed, for example, in Japanese Patent Laid-open No. 64-34670.
This sandblasting method is capable of processing the surface of a work at a relatively high processing rate and is advantageous in plant and equipment investment, however, the sandblasting method is unsatisfactory when applied to processing the surface of a semiconductor wafer in patterning accuracy and the surface condition of the processed surface because the particle size of the particles employed in the sandblasting method at the minimum is on the order of 16 .mu.m.
Those previously proposed various etching methods are unsatisfactory in either processing rate or processing accuracy, and the improvement of those etching methods has been desired.
A sputtering process, a flame spraying process and a chemical vapor deposition process (CVD) are known thin film forming techniques.
The sputtering process ejects atoms of a target from the target by bombarding the surface of the target in a vacuum with accelerated ions of an inert gas, such as Ar gas, to make the ejected atoms deposit over the surface of a substrate in a thin film. The density of the thin film thus formed by the sputtering process is quite satisfactory. However, the deposition rate of the sputtering process is low, for example, on the order of 0.006 .mu.m/min in depositing a thin film of alumina, the sputtering process needs a high vacuum and an expensive apparatus, and the substrate is heated to a relatively high temperature during the sputtering process.
The flame spraying process melts a powder material, such as a ceramic powder, for forming a film under the atmospheric pressure or a reduced pressure by the heat of a plasma or a burner, and then sprays the melted material over a substrate to form a film. Although the flame spraying process is featured by its high deposition rate, the flame spraying process forms many voids in the film, and the flame spraying process is applicable only to forming a film on a heat-resistant substrate because the surface of the substrate is heated at a considerably high temperature.
The chemical vapor deposition process makes source gases interact by the heat of a plasma to deposit a thin film of a reaction product over a substrate. The chemical vapor deposition process, similarly to the sputtering process, is capable of forming a very dense film. However, the chemical vapor deposition process forms a film at a relatively low deposition rate and requires a space of a high vacuum, which is disadvantageous in respect of plant and equipment investment. Furthermore, since the substrate is heated to a temperature in the range of 250 to 600.degree. C., the chemical vapor deposition process is applicable only to forming a film on a heat-resistant substrate.
Thus, the conventional film forming techniques are unsatisfactory in processing speed and subject to restrictions on the substrate on which a film is to be formed. Accordingly, fundamental improvement in the conventional film forming techniques has been desired.
As stated above, the conventional techniques for etching and deposition need a number of improvements concerning processing speed, processing accuracy, manufacturing cost and maintenance, and the development of a new processing technique has been anticipated.